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Commit 71c7e4f6 authored by Dominik Laskowski's avatar Dominik Laskowski
Browse files

FTL: Allow Concat of bool and char 

Also, allow references to integral types.

Bug: 185536303
Test: ftl_test
Change-Id: Ic9be008ed7f72ecdb7a369b01bc5a8235b35ac2c
parent edfce733

include/ftl/concat.h

+3 −1
Original line number Diff line number Diff line
@@ -20,7 +20,9 @@ 


namespace android::ftl {



// Lightweight (not allocating nor sprintf-based) concatenation.

// Lightweight (not allocating nor sprintf-based) concatenation. The variadic arguments can be

// values of integral type (including bool and char), string literals, or strings whose length

// is constrained:

//

//   std::string_view name = "Volume";

//   ftl::Concat string(ftl::truncated<3>(name), ": ", -3, " dB");

include/ftl/details/concat.h

+32 −4
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <functional>

#include <string_view>



#include <ftl/details/type_traits.h>

#include <ftl/string.h>



namespace android::ftl::details {
@@ -26,16 +27,42 @@ namespace android::ftl::details { 
template <typename T, typename = void>

struct StaticString;



// Booleans.

template <typename T>

struct StaticString<T, std::enable_if_t<std::is_integral_v<T>>> {

  static constexpr std::size_t N = to_chars_length_v<T>;

struct StaticString<T, std::enable_if_t<is_bool_v<T>>> {

  static constexpr std::size_t N = 5;  // Length of "false".



  explicit StaticString(T v) : view(to_chars(buffer, v)) {}

  explicit constexpr StaticString(bool b) : view(b ? "true" : "false") {}



  to_chars_buffer_t<T> buffer;

  const std::string_view view;

};



// Characters.

template <typename T>

struct StaticString<T, std::enable_if_t<is_char_v<T>>> {

  static constexpr std::size_t N = 1;



  explicit constexpr StaticString(char c) : character(c) {}



  const char character;

  const std::string_view view{&character, 1u};

};



// Integers, including the integer value of other character types like char32_t.

template <typename T>

struct StaticString<

    T, std::enable_if_t<std::is_integral_v<remove_cvref_t<T>> && !is_bool_v<T> && !is_char_v<T>>> {

  using U = remove_cvref_t<T>;

  static constexpr std::size_t N = to_chars_length_v<U>;



  // TODO: Mark this and to_chars as `constexpr` in C++23.

  explicit StaticString(U v) : view(to_chars(buffer, v)) {}



  to_chars_buffer_t<U> buffer;

  const std::string_view view;

};



// Character arrays.

template <std::size_t M>

struct StaticString<const char (&)[M], void> {

  static constexpr std::size_t N = M - 1;
@@ -50,6 +77,7 @@ struct Truncated { 
  std::string_view view;

};



// Strings with constrained length.

template <std::size_t M>

struct StaticString<Truncated<M>, void> {

  static constexpr std::size_t N = M;

include/ftl/details/type_traits.h

+6 −0
Original line number Diff line number Diff line
@@ -24,4 +24,10 @@ namespace android::ftl::details { 
template <typename U>

using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<U>>;



template <typename T>

constexpr bool is_bool_v = std::is_same_v<remove_cvref_t<T>, bool>;



template <typename T>

constexpr bool is_char_v = std::is_same_v<remove_cvref_t<T>, char>;



}  // namespace android::ftl::details

libs/ftl/concat_test.cpp

+17 −0
Original line number Diff line number Diff line
@@ -28,8 +28,25 @@ TEST(Concat, Example) { 
  EXPECT_EQ(string.c_str()[string.size()], '\0');

}



TEST(Concat, Characters) {

  EXPECT_EQ(ftl::Concat(u'a', ' ', U'b').str(), "97 98");

}



TEST(Concat, References) {

  int i[] = {-1, 2};

  unsigned u = 3;

  EXPECT_EQ(ftl::Concat(i[0], std::as_const(i[1]), u).str(), "-123");



  const bool b = false;

  const char c = 'o';

  EXPECT_EQ(ftl::Concat(b, "tt", c).str(), "falsetto");

}



namespace {



static_assert(ftl::Concat{true, false, true}.str() == "truefalsetrue");

static_assert(ftl::Concat{':', '-', ')'}.str() == ":-)");



static_assert(ftl::Concat{"foo"}.str() == "foo");

static_assert(ftl::Concat{ftl::truncated<3>("foobar")}.str() == "foo");